The present invention relates to optical pigtail assemblies and more specifically to a laser pigtail assembly for use with a multimode laser and its method of manufacture.
Optical pigtail assemblies are used for coupling the output from an optical source, such as a light emitting diode, laser diode, and the like, to an optical waveguide, such as a fiber optic cable or the like. The optical waveguide is positioned within the pigtail assembly for maximum optical power transfer from the optical source to the waveguide.
In a typical single mode laser pigtail assembly, the laser diode, usually contained in a metal can, is soldered or laser welded to a base member. A gradient index lens, such as a plano-convex lens or a plano-plano lens, is fixedly positioned adjacent to a window in the laser diode can. When using a plano-convex lens, the convex end of the lens is positioned toward the laser to magnify and focus the output of the laser diode. A cap member is placed over the laser diode and gradient index lens. The cap member has a central aperture into which is secured an optical fiber. The optical fiber can be placed directly into the aperture or, alternately, the fiber can be placed in a ferrule and then secured in the aperture. The optical fiber and the cap member are positioned vertically and horizontally with respect to the output of the laser diode for maximum optical power transfer from the laser diode to the optical fiber and then secured.
An alternative method of manufacturing such a laser pigtail assembly is to use a long term curing epoxy to assemble the pigtail assembly parts. The manufacturing steps are similar to the soldering or laser welding process in that the optical fiber is aligned with respect to the laser diode for maximum power transfer. In the long term curing epoxy process, a layer of epoxy on the order of 50 microns, is applied between the parts being assembled. The assembled parts are then set aside until the epoxy is cured. Low volume output is one disadvantage of this process since substantial curing time is required for each assembly step. In addition, both the epoxy process and the laser welding process require large capital investments. For the epoxy process, a humidity and vibration controlled room is required while the laser welding process requires expensive laser welding machines.
What is needed is a laser pigtail assembly with high optical power coupling efficiency and good thermal performance that is manufactured using a high output and low cost method that does not require large capital investments.